In oilfield industry porosity is the key value for determining the amount of hydrocarbon resources for a particular reservoir. There are a number of methods for measuring porosity of core samples. Standard ones include gas saturation with pressure-volume control, liquid saturation with weighting, petrographic analysis of thin sections (see for example U.S. Pat. No. 4,562,726, U.S. Pat. No. 2,840,717). Main disadvantage of listed methods is that they are relatively time consuming and operator dependent. Petrographic analysis of thin sections might provide absolutely non-representative results as it deals with finite number (usually 1 or 2) of 2D sections of the real 3D rock sample. Preparation of these sections might be destructive and this decreases the adequacy of 2D thin section porosity interpretation even more.